ParallaxImageView.java

/*
 *    Calendula - An assistant for personal medication management.
 *    Copyright (C) 2016 CITIUS - USC
 *
 *    Calendula is free software; you can redistribute it and/or modify
 *    it under the terms of the GNU General Public License as published by
 *    the Free Software Foundation; either version 3 of the License, or
 *    (at your option) any later version.
 *
 *    This program is distributed in the hope that it will be useful,
 *    but WITHOUT ANY WARRANTY; without even the implied warranty of
 *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *    GNU General Public License for more details.
 *
 *    You should have received a copy of the GNU General Public License
 *    along with this software.  If not, see <http://www.gnu.org/licenses/>.
 */

package es.usc.citius.servando.calendula.util.view;


import android.content.Context;
import android.graphics.Canvas;
import android.util.AttributeSet;
import android.widget.ImageView;


public class ParallaxImageView extends ImageView {

    private int mCurrentTranslation;

    public ParallaxImageView(Context context) {
        super(context);
    }

    public ParallaxImageView(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

    public ParallaxImageView(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
    }

    public void updateParallax(){
        int[] ls = new int[2];
        getLocationOnScreen(ls);
        float top = (float)ls[1];
        if(top > 0) {
            mCurrentTranslation = -(int)(top*1.5);
            invalidate();
        }
    }

    @Override
    public void draw(Canvas canvas) {
        canvas.save();
        canvas.translate(0, mCurrentTranslation);
        super.draw(canvas);
        canvas.restore();
    }
}